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Echolocation and Acoustics

Category: General Article

Back to Creep into the DEEPEND

Wednesday, June 8, 2016

Summary: Dr. Joe Warren explains how science imitates nature thorugh the use of high technology which locates animals using sound waves.

My name is Joe Warren. I count animals and I do it using sound. After reading that, your first thought might be, “Cool!” Your second and third thoughts might be, “Why and how?”

Let’s start with the why. If you wanted to count how many fish were in an aquarium tank, which of your senses — sight, taste, touch, hearing, or smell — would you use?

Most of us would say sight. That would work. But what if I asked you to count the fish in the tank at night with no lights on. Then it would much more difficult.

The only light in the ocean is from the sun and moon. That light can only travels down so far. Once you get a couple of soccer fields deep, the ocean is dark. Though it is dark 24/7, we know that many animals live in the deep. To understand this important ecosystem, we need to know how many animals live in the dark sea and where they live.

How do I count the animals? The technology I use to “see” in to the deep sea is called an “echosounder.” The echosounder uses sound to see, similar to the echolocation of a dolphin or bat.

Like a dolphin’s echolocation, the echosounder sends out a beam of sound. When the sound hits something, it echoes or bounces back.

A dolphin uses the returning sounds to find food or its way in the dark sea. With echolocation the dolphin can determine how far away something, is, how fast it is moving, which way it’s moving, and so much more.

How does the echosounder work? We transmit a short pulse of sound. It’s so short it sounds like a “snap.” The sound travels down toward the ocean bottom. Like a dolphin, we listen for echoes as the sound bounces off objects in the water column. We measure how long it takes for the ups and downs of the sea continued the echo to return to us.

From that echo we can determine how deep the fish are located. Usually, the strongest echo comes from the seafloor, but if there are marine animals, they’ll produce echoes as well.

Many ocean animals live deeper when the sunrises. Then when the sun sets, they swim up toward the surface. This is daily up and down movement is called, vertical migration. Vertical migration happens every day all over the world, making it the largest migration on Earth. During the day, these animals are very deep in the ocean (about a half mile below the surface). Using our echosounder, we can watch these animals move up and down in the ocean.

If you take a look at the illustrated diagram shown above, you can better understand the cyclical movements of these animals during vertical migration. You can download a labeled poster-sized version of this diagram from the right sidebar which better explains the process and includes some of the tech we use for DEEPEND.

Thanks for joining us.

Dr. Joe Warren, Team Acoustics and Deep-Sea Explorer

Related Features: Dr. Tamara Frank and the Mysteries of Vertical Migration

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Dr. Tamara Frank and Vertical Migration

Dr. Tamara Frank, an expert in the deep sea and DEEPEND member, discusses the amazing phenomenon of vertical migration — the largest movement of animal life on Earth.

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Creep Into the DEEPEND is a WhaleTimes, Inc. Virtual Research Mission, in cooperation with the DEEPEND Consortium and the Oceanscape Network. For more information visit whaletimes.org

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